1. Field of the Invention
The present invention relates to an apparatus and method for convenient purging of air from a brake master cylinder assembly, while detached from an automobile, thus filling the master cylinder with brake fluid.
2. Background Information
Before a master cylinder of a brake system can be properly and safely used in a motor vehicle, it must be purged of air or other gasses, and filled with brake fluid. The purging of air, often referred to as “bleeding,” is performed when the vehicle is first manufactured, and may also be required periodically during the service life of the vehicle. In either case, purging of air is required for successful operation under the pressure normally imparted to the system to operate the brakes.
Bleeding may be performed while a master cylinder is attached to a vehicle, or alternatively, while a master cylinder is free-standing. In the latter approach, the master cylinder is typically placed within a fixture, such as a vise. Flow conduits are connected to fluid pressure outlets on the cylinder, typically one or two in number, and the free ends of the conduits are positioned to discharge pressurized brake fluid from a working chamber of the master cylinder (bore) back into a master cylinder reservoir. A piston in the master cylinder is repeatedly stroked to pressurize brake fluid within the bore, and force the brake fluid outwardly through the outlets and back into the reservoir. The result of such repeated pressurization of the braking fluid is the expulsion of any entrained gas bubbles within the master cylinder.
Typically, a mechanic performing the above procedure may employ a common tool such as a Phillips head screwdriver to depress the piston. However such a procedure suffers from the fact that an operator may fail to utilize proper force during each pressurization. During a typical bleeding process, a large degree of leverage is required to properly depress a piston, causing an operator to fail to depress the piston in a consistent manner during each pressurization. Additionally, the tool employed may slip from the operator's hand, or the master cylinder may rotate or slip within the vise, due to improper or inadequate gripping.
Alternatively, in the former case where a master cylinder is already mounted within a vehicle, bleeding typically requires an operator to mechanically depress the mechanism leading from the brake pedal to the master cylinder piston, while additionally monitoring the presence of bubbles within the system.
In both of the aforementioned cases, an operator must manually actuate the master cylinder piston while also arranging to pinch off the bleed line or lines during each retraction of the piston, so as to prevent backflow of the brake fluid through the bleed lines, a cumbersome process at best.
In light of the forgoing, it is clear that a need exists for a device and method to more conveniently perform bleeding of a master cylinder.